1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member.
2. Description of the Related Art
An electrophotographic photosensitive member is generally used together with a developer in a series of electrophotographic image forming processes including charging, exposure, development, transfer, and cleaning. In the processes, toner in the developer is developed onto the surface of the electrophotographic photosensitive member by a developing unit, and is then transferred onto a transfer material by a transferring unit. However, toner remaining on the surface of the electrophotographic photosensitive member even after the transferring step (hereinafter referred to as “transfer residual toner”) is present. The transfer residual toner is removed from the surface of the electrophotographic photosensitive member by a cleaning unit in an electrophotographic image forming process using the cleaning unit. The cleaning unit is, for example, a method involving bringing a cleaning blade composed of an elastic body such as a urethane rubber into contact with the electrophotographic photosensitive member to scrape the transfer residual toner. Alternatively, for example, a method involving the use of a fur brush or a method involving the combined use of the cleaning blade and the fur brush is available, and a method involving the use of the cleaning blade has been widely employed because of its simplicity and effectiveness.
An electrophotographic photosensitive member in which a photosensitive layer (organic photosensitive layer) using an organic material as a photoconductive substance (a charge generation substance or a charge transport substance) is formed on a support, the so-called organic electrophotographic photosensitive member, has been currently in widespread use from the viewpoints of, for example, its low price and high productivity. Of those organic electrophotographic photosensitive members, a mainstream organic electrophotographic photosensitive member is of a lamination type photosensitive layer obtained by superimposing: a charge generating layer containing a charge generation substance such as a photoconductive dye or a photoconductive pigment; and a charge transporting layer containing a charge transport substance such as a photoconductive polymer or a photoconductive low-molecular-weight compound. The mainstream organic electrophotographic photosensitive member has been used because of its advantages including high sensitivity and the diversity of material designs.
Active investigations have been currently conducted on the improvement of the layer serving as the outermost surface of an electrophotographic photosensitive member (hereinafter referred to as “surface layer”) with a view to improving the durability of the electrophotographic photosensitive member or suppressing the degradation of the quality of an image formed with the electrophotographic photosensitive member irrespective of whether the electrophotographic photosensitive member is of a single-layered type or a lamination type. To be specific, investigations have been made into, for example, the improvement of a resin for the surface layer and the addition of a filler or water repellent material as approaches from a material aspect from the viewpoints of, for example, an increase in strength of the surface layer and the impartment of high releasability or sliding property to the surface layer.
Meanwhile, investigations have been made into an improvement in transfer efficiency of the electrophotographic photosensitive member, the suppression of image defects due to, for example, cleaning failure, and the solution of problems such as the chattering and turn-up of a cleaning blade by moderate roughening of the surface layer as approaches from a physical aspect. The chattering of the cleaning blade is a phenomenon in which the cleaning blade vibrates owing to an increase in frictional resistance between the cleaning blade and the peripheral surface of an electrophotographic photosensitive member. In addition, the turn-up of the cleaning blade is a phenomenon in which the cleaning blade is reversed in the direction in which the electrophotographic photosensitive member moves.
Various techniques for roughening the surface layer by a physical means are available. For example, Patent Document 1 discloses a technique for causing the surface roughness (roughness of the peripheral surface) of an electrophotographic photosensitive member to fall within a specified range for facilitating the separation of a transfer material from the surface of the electrophotographic photosensitive member. To be specific, Patent Document 1 discloses a method of roughening the surface of an electrophotographic photosensitive member in an orange peel fashion by controlling a drying condition upon formation of the surface layer of the electrophotographic photosensitive member. In addition, Patent Document 2 discloses a technique for roughening the surface of an electrophotographic photosensitive member by incorporating a particle into the surface layer of the electrophotographic photosensitive member. In addition, Patent Document 3 discloses a technique for roughening the surface of an electrophotographic photosensitive member by abrading the surface of the surface layer of the electrophotographic photosensitive member with a metallic wire brush. In addition, Patent Document 4 discloses a technique in which a specific cleaning means and specific toner are used and the surface of an organic electrophotographic photosensitive member is roughened. The document aims to solve, with the technique, the reversal (turning-up) of a cleaning blade and the chipping of an edge portion of the cleaning blade which become problems when the organic electrophotographic photosensitive member is used in an electrophotographic apparatus having a specific process speed or higher. In addition, Patent Document 5 discloses a technique for roughening the surface of an electrophotographic photosensitive member by abrading the surface of the surface layer of the electrophotographic photosensitive member with a filmy abrasive. In addition, Patent Document 6 discloses a technique for roughening the peripheral surface of an electrophotographic photosensitive member by blast treatment. However, details about the surface shapes of the electrophotographic photosensitive members disclosed in Patent Documents 1 to 6 described above are unknown.
Meanwhile, a technique for forming predetermined dimple shapes on the surface of an electrophotographic photosensitive member by controlling the surface shape of the electrophotographic photosensitive member has also been disclosed (see Patent Document 7). In addition, for example, Patent Document 8 discloses a technique for subjecting the surface of an electrophotographic photosensitive member to compression molding with a stamper having well-like irregularities. The technique is expected to be extremely effective against the above-mentioned problems from the following viewpoint of forming independent irregularities on the surface of the electrophotographic photosensitive member with higher controllability than that the techniques disclosed in Patent Documents 1 to 6 described above. According to Patent Document 8, the formation of well-like irregularities having a length or pitch of 10 to 3,000 nm on the surface of an electrophotographic photosensitive member improves the releasability of toner, whereby the nip pressure of a cleaning blade can be reduced, and as a result, the wear of the electrophotographic photosensitive member can be reduced.
When a cleaning blade is used as the cleaning means, for example, such members as described below are generally used in combination with the cleaning blade. First, a sheet member is used, which is placed on the upstream side in the direction in which the electrophotographic photosensitive member moves with respect to the cleaning blade so as to come in weak contact with the surface of the electrophotographic photosensitive member for scooping transfer residual toner scraped by the cleaning blade. A seal member for sealing gaps among the electrophotographic photosensitive member, the cleaning blade, the sheet member, and a cleaning frame is also used in combination at both edge portions in the longitudinal direction of the cleaning blade. The seal member serves to prevent the transfer residual toner (recovered toner) scraped by the cleaning blade from leaking out of a recovered toner container from the gap portions.
However, when the dimensions of a portion where the seal member comes in close contact with the cleaning frame or the cleaning blade vary, a gap arises between the seal member and the cleaning frame or the cleaning blade which should essentially be in close contact with each other, and a problem occurs in that the recovered toner leaks little by little out of the gap during printing. In addition, the seal member must be precisely set in the cleaning frame lest such leakage of the recovered toner should occur. Accordingly, there has been a problem in terms of setting workability as well.
To cope with those problems, efforts have been made to enhance the sealing property and setting property of the seal member by improving the seal member (see Patent Document 9).
Patent Document 1: Japanese Patent Application Laid-Open No. S53-092133
Patent Document 2: Japanese Patent Application Laid-Open No. S52-026226
Patent Document 3: Japanese Patent Application Laid-Open No. S57-094772
Patent Document 4: Japanese Patent Application Laid-Open No. H01-099060
Patent Document 5: Japanese Patent Application Laid-Open No. H02-139566
Patent Document 6: Japanese Patent Application Laid-Open No. H02-150850
Patent Document 7: International Publication No. WO2005/093518
Patent Document 8: Japanese Patent Application Laid-Open No. 2001-066814
Patent Document 9: Japanese Patent Application Laid-Open No. H08-202242